This Daring Fly Swims in a Shimmering Bubble Shield

Covered in a shiny bubble, the alkali fly scuba dives into the harsh waters of California’s Mono Lake. Thanks to an abundance of hair and water-repellent wax, this remarkable insect remains dry while embarking on a quest for tasty algae and a place to lay its eggs.

TRANSCRIPT

This fly is the Jacques Cousteau of flies. It dives where no other insect dares, in its very own scuba gear.

It risks it all for food and a place to lay its eggs.

The alkali fly thrives in waters three times saltier than the ocean, here in California’s Mono Lake. 

It lives among these otherworldly towers of limestone deposits called tufas. 

Those same minerals make the water inhospitable for almost every other form of life. Like if someone made a soup of table salt, baking soda, and soda ash, an abrasive stain remover. 

But the alkali fly? It loves it. Scientists call this kind of creature an extremophile. It survives in an extreme environment.

As a larva, it spends all its time underwater. It gets oxygen through its skin.

These special kidneys, called lime glands, pump excess salts out of its body. It’s a process called osmoregulation.

When it grows up, it gets its wings, but it loses those lime glands and can’t breathe under the surface.

So this extremophile employs an extreme solution: a shimmering bubble shield enclosing its entire body. 

The only things sticking out are its eyes … and its claws.

As it dives from the surface, it captures air between its body and hairs, like its very own oxygen tank. And the fly isn’t actually getting wet.

It can do this thanks to its charming looks. It’s far hairier than your average fly. 

Check out its shaggy wings, fluffy legs, and bristly abdomen. 

These hairs, and the fly’s body, are covered in water-repellent wax. It’s a lot of product, but these waxy hairs are crucial to the fly’s survival. 

Here’s an animal that doesn’t have as many hairs: This red ant wandered too close to the lake’s edge. Now, it can handle some amount of freshwater, but the mineral-rich Mono Lake water bogs it down.

Mono Lake’s water is some of the wettest water in the world. Yeah, you heard me right.

You see, all water sticks to itself; that’s why rain comes down in neat droplets. But the minerals in Mono Lake water make it even stickier. It feels slippery and soapy.

Check out the wing of this house fly when it touches a droplet of pure water. The wing pulls away from the drop easily. But when it touches water with the same compounds as Mono Lake? It sticks.

So your standard fly, frog, even fish avoids the lake at all costs.

The only other life down here is brine shrimp and one type of microscopic worm. That leaves nearly all the delicious algae for the alkali fly. 

The fly sticks out its proboscis and slurps it up where the algae collects on tufas. 

But this diving fly is not invincible. The water levels of Mono Lake are getting lower. We divert water from the streams that feed the lake, and rising temperatures mean it’s drying up faster than before. 

This makes the lake more salty, and those larvae that spend their days underwater can only handle so much. Fewer of them are growing into adults.

Maybe you’re thinking, “So what, it’s just a few flies!” But these swarms help feed millions of birds as they migrate across the Americas.

While the alkali fly may seem audacious, even indestructible, it still relies on a delicate balance to survive. 

Hey, Deep peeps, want to learn more about Mono Lake’s world-famous tufa towers? 

Head over to PBS Terra’s new science show, Untold Earth. You’ll uncover the lake’s primordial secrets, and meet the people working to save it for future generations. See you there!